Idaho National Laboratory and Argonne National Laboratory are seeking information from organizations capable of providing long-duration energy storage (LDES) battery systems for benchmark performance testing at their facilities. Acceptable systems include rechargeable electrochemical batteries in module-scale (100–150 kWh, 10–15 kW over ten hours) and full-scale (1000–1500 kWh, 100–150 kW over ten hours) configurations, with a 15-year lifetime and data publication allowed. Unacceptable technologies include lithium-ion, lead-acid, redox flow, and non-rechargeable systems. Delivery timelines are approximately 3 months after final design acceptance for modules to INL and approximately 6 months for the full-scale system to ANL, with commissioning and site acceptance testing to follow. No budget amounts are specified in this description.